The present invention concerns electric motors used with a motor vehicle actuator.
The invention advantageously finds use in closed electric motors that dissipate heat energy, such as wiper motors, clutch controls, the windshield motors of motor vehicles, and electric control motors of sunroofs or of seats. The invention applies to electric motors of the synchronous type, asynchronous types, or others.
Classically, the stator of an electric motor with direct current comprises a steel frame which serves to support the magnets, which assures the seal of the motor, allowing one to close the magnetic flux and assures a good removal of the heat generated in the inductor via conduction, convection and radiation.
In certain applications, it is desirable to have at one""s disposal very small electric motors, allowing higher rotational speeds and transmitting significant engine torque, for the wiping and the control of the wiping of a vehicle.
In order to do this, one knows, in document FR-2.432.790, electric motor structures in which the frame of the stator is in a non-magnetizable material, such as xe2x80x9czamacxe2x80x9d, and carries a soft-iron ring-shaped element that allows the flux of the magnetic field to close.
This frame is made of up two half boxes closed onto each other according to a contact plane what passes by the axis of the motor. These half boxes present openings in which the stator magnets are received, such that the said frame is not at all sealed and the motor is well ventilated.
A technical problem encountered while one seeks to create compact and water- and dust-proof electric motors is that of the evacuation of the heat dissipated by the inductor because, while one tries to diminish the size of the motor, one must increase the rotational speed in order to transmit an equivalent engine torque, while leads to an increase of the heat to emit.
The goal of the invention is to resolve this problem in a simple and economic manner by improving the thermal exchanges.
The invention proposes such an electric motor, to be used in a motor vehicle, that comprises a rotor provided with a coil having first and second radial ends, and mounted rotatingly in a hollow frame formed of two hollow parts directly mounted on each other and having end walls. The two parts are made of good heat conducting material, and the frame bears induction means. The frame is sealed, and the two parts are two pieces assembled transversally one onto the other. The end wall of each part is continuously adjacent to one of the first and second ends of the coil.
In these conditions, the radiation and thermal convection of the ends of the coil are directly transmitted to the end walls and evacuated in the optimal method.
In addition, the plane of the joint or the assembly of the two pieces is implanted outside of the bearings supporting the motor axis in such a way that the bearings are carefully arranged. Also, the two pieces are not necessarily the same, for example, one of the pieces can have a thickness considerably greater than the other. However, the assembly plane of the two pieces can be a simple sturdier flange.
Thanks to transversal mounting of the pieces of the frame, direct access to the parts making up the motor is facilitated by removing one of the pieces of the frame.
Such a motor is advantageously completed by the different following characteristics taken individually or according to all of their possible combinations:
the walls of the end envelope roughly in the shape of buns, made up from the ends of the coil, in order to still prefer the thermal exchanges;
the interior surfaces of the end walls of the two pieces of the frame are centrally shaped with a bowl shape that limits the ends of the rotor coil that are adjacent to the walls;
the heat conducting material is not magnetic and is advantageously chosen from the group containing xe2x80x9czamac,xe2x80x9d aluminum, and magnesium in order to reduce the weight of the motor and to facilitate its creation via casting;
variably, the material is magnetic or magnetizable, such as steel;
one of the two pieces of the frame is a piece with at least one part gear box casing of the actuator to which the said motor corresponds;
at least one of the two pieces of the frame comprises an end of the wall and a radial orientation portion that contains, on the outside, elements that contribute to the increase in thermal changes with ambient air;
at least one of the two pieces of the frame comprises cooling fins;
at least one of the two pieces of the frame comprises fixation lugs that facilitate the thermal changes via conduction and the dismantling of the piece devoid of the fixation lugs;
at least one or the other of the two pieces of the frame comprises a wall end and circumferential part; and
the two pieces are in different materials.